Embodiments of the present invention relate to a method for measuring current in an electric network. Measuring the current consumption in an electric network enables an energy diagnosis to be made. By offering the user the possibility of monitoring its current consumption item by item, called “electrical use”, significant savings can be made.
New thermal regulations encourage the use of current consumption measuring devices in service and residential buildings, by providing, in each electric board, for the estimation and the display of the consumption of the various connected appliances (heating, cooling, hot water production, lighting, cooking, sockets, and the like).
Several methods for estimating electrical use are known. Certain methods involve a direct measurement by installing an electrical use submeter in the electric board, while others involve an indirect measurement by analyzing the global load curve on the network, and correlating it with usage parameters of the various appliances connected.
Indirect methods provide an estimation of the use by analyzing the load curve at the input point of the electric board. Their scope of application is reduced and is limited to loads that switch only a few times a day. A correlation-based estimation algorithm is used that is unreliable when the loads have a current consumption that varies continuously, for example an air conditioner, a heat pump, or a variable drive motor, or that switch very often with time intervals of a few seconds. These methods are thus difficult to apply to the service sector or retail outlets.
The methods involving a direct measurement require installing sub-metering modules in the electric board, each comprising a current sensor and which must be arranged in series with the protection circuit breakers. Circuit breakers integrating devices for measuring current have also been suggested.
The methods involving a direct measurement are difficult to implement and expensive when they must be implemented in an existing installation. In this case, it is necessary to change the wiring of the electric board, or even to change the board to enable the sub-metering modules or new circuit breakers to be installed. The installation cost then greatly exceeds the savings to be made for private individuals, a small store, or a small service building. This method is thus rarely implemented.
To reduce the cost price of the metering modules, circuit breakers equipped with a current sensor with a microelectromechanical system (MEMS), as described for example in International Patent Publication No. WO 2008 042 483, have been suggested. However, conventional circuit breakers are generally preferred due to their low cost price. Moreover, circuit breakers equipped with current sensors are intended for the new property market and do not find any opening in existing buildings due to their high purchase and installation costs.
International Patent Publication No. WO 01/50142 also describes metering modules based on MEMS sensors that are arranged around electric wires. These sensors must be linked to an electronic measurement circuit and the global cost price is high.
Therefore, it could be desirable to provide a method for measuring current in an electric network that has a low cost price and is easy to adapt to an existing electric installation, without the need to replace its components.